W-CDMA (Wideband Code Division Multiple Access) is a radio interface for IMT-2000 (International Mobile Communication), which was standardized for use as the 3rd generation wireless mobile telecommunication system. It provides a variety of services such as voice services and multimedia mobile communication services in a flexible and efficient way. The standardization bodies in Japan, Europe, USA, and other countries have jointly organized a project called the 3rd Generation Partnership Project (3GPP) to produce common radio interface specifications for W-CDMA.
The standardized European version of IMT-2000 is commonly called UMTS (Universal Mobile Telecommunication System). The first release of the specification of UMTS has been published in 1999 (Release 99). In the mean time several improvements to the standard have been standardized by the 3GPP in Release 4 and Release 5 and discussion on further improvements is ongoing under the scope of Release 6.
The dedicated channel (DCH) for downlink and uplink and the downlink shared channel (DSCH) have been defined in Release 99 and Release 4. In the following years, the developers recognized that for providing multimedia services—or data services in general—high speed asymmetric access had to be implemented. In Release 5 the high-speed downlink packet access (HSDPA) was introduced. The new high-speed downlink shared channel (HS-DSCH) provides downlink high-speed access to the user from the UMTS Radio Access Network (RAN) to the communication terminals, called user equipments in the UMTS specifications.
UMTS Architecture
The high level R99/4/5 architecture of Universal Mobile Telecommunication System (UMTS) is shown in FIG. 1 (see 3GPP TR 25.401: “UTRAN Overall Description”, available from http://www.3gpp.org). The network elements are functionally grouped into the Core Network (CN) 101, the UMTS Terrestrial Radio Access Network (UTRAN) 102 and the User Equipment (UE) 103. The UTRAN 102 is responsible for handling all radio-related functionality, while the CN 101 is responsible for routing calls and data connections to external networks. The interconnections of these network elements are defined by open interfaces (Iu, Uu). It should be noted that UMTS system is modular and it is therefore possible to have several network elements of the same type.
In the sequel two different architectures will be discussed. They are defined with respect to logical distribution of functions across network elements. In actual network deployment, each architecture may have different physical realizations meaning that two or more network elements may be combined into a single physical node.
FIG. 2 illustrates the current architecture of UTRAN. A number of Radio Network Controllers (RNCs) 201, 202 are connected to the CN 101. Each RNC 201, 202 controls one or several base stations (Node Bs) 203, 204, 205, 206, which in turn communicate with the user equipments. An RNC controlling several base stations is called Controlling RNC (C-RNC) for these base stations. A set of controlled base stations accompanied by their C-RNC is referred to as Radio Network Subsystem (RNS) 207, 208. For each connection between User Equipment and the UTRAN, one RNS is the Serving RNS (S-RNS). It maintains the so-called Iu connection with the Core Network (CN) 101.
Enhanced Uplink Dedicated Channel (E-DCH)
Uplink enhancements for Dedicated Transport Channels (DTCH) were studied by the 3GPP Technical Specification Group RAN (see 3GPP TR 25.896: “Feasibility Study for Enhanced Uplink for UTRA FDD (Release 6)”, available at http://www.3gpp.org). Since the use of IP-based services become more important, there is an increasing demand to improve the coverage and throughput of the RAN as well as to reduce the delay of the uplink dedicated transport channels. Streaming, interactive and background services could benefit from this enhanced uplink.
One enhancement is the usage of adaptive modulation and coding schemes (AMC) in connection with Node B controlled scheduling, thus an enhancement of the Uu interface. In the existing R99/R4/R5 system the uplink maximum data rate control resides in the RNC. By relocating the scheduler in the Node B the latency introduced due to signaling on the interface between RNC and Node B may be reduced and thus the scheduler may be able to respond faster to temporal changes in the uplink load. This may reduce the overall latency in communications of the user equipment with the RAN. Therefore Node B controlled scheduling is capable of better controlling the uplink interference and smoothing the noise rise variance by allocating higher data rates quickly when the uplink load decreases and respectively by restricting the uplink data rates when the uplink load increases. The coverage and cell throughput may be improved by a better control of the uplink interference.
Another technique, which may be considered to reduce the delay on the uplink, is introducing a shorter TTI (Transmission Time Interval) length for the E-DCH compared to other transport channels. A transmission time interval length of 2 ms is currently investigated for use on the E-DCH, while a transmission time interval of 10 ms is commonly used on the other channels. Hybrid ARQ, which was one of the key technologies in HSDPA, is also considered for the enhanced uplink dedicated channel. The Hybrid ARQ protocol between a Node B and a user equipment allows for rapid retransmissions of erroneously received data units, and may thus reduce the number of RLC (Radio Link Control) retransmissions and the associated delays. This may improve the quality of service experienced by the end user.
To support enhancements described above, a new MAC sub-layer is introduced which will be called MAC-e in the following (see 3GPP TSG RAN WG1, meeting #31, Tdoc R01-030284, “Scheduled and Autonomous Mode Operation for the Enhanced Uplink”).
The entities of this new sub-layer, which will be described in more detail in the following sections, may be located in user equipment and Node B. On user equipment side, the MAC-e performs the new task of multiplexing upper layer data (e.g. MAC-d) data into the new enhanced transport channels and operating HARQ protocol transmitting entities.
Further, the MAC-e sub-layer may be terminated in the S-RNC during handover at the UTRAN side. Thus, the reordering buffer for the reordering functionality provided may also reside in the S-RNC.
E-DCH MAC Architecture—UE side
FIG. 3 shows the exemplary overall E-DCH MAC architecture on UE side. A new MAC functional entity, the MAC-e/es, is added to the MAC architecture of Release '99.
The MAC interworking on the UE side is illustrated in FIG. 4. There are M different data flows (MAC-d) carrying data packets from different applications to be transmitted from UE to Node B. These data flows can have different QoS requirements (e.g. delay and error requirements) and may require different configuration of HARQ instances. Each MAC-d flow represents a logical unit to which specific physical channel (e.g. gain factor) and HARQ (e.g. maximum number of retransmissions) attributes can be assigned.
Further, MAC-d multiplexing is supported for an E-DCH, i.e. several logical channels with different priorities may be multiplexed onto the same MAC-d flow. Data of multiple MAC-d flows can be multiplexed in one MAC-e PDU (protocol data unit). In the MAC-e header, the DDI (Data Description Indicator) field identifies logical channel, MAC-d flow and MAC-d PDU size. A mapping table is signaled over RRC, to allow the UE to set DDI values. The N field indicates the number of consecutive MAC-d PDUs corresponding to the same DDI value.
The MAC-e/es entity is depicted in more detail in FIG. 5. The MAC-es/e handles the E-DCH specific functions. The selection of an appropriate transport format for the transmission of data on E-DCH is done in the E-TFC Selection entity, which represents a function entity. The transport format selection is done according to the scheduling information (Relative Grants and Absolute Grants) received from UTRAN via L1, the available transmit power, priorities, e.g. logical channel priorities. The HARQ entity handles the retransmission functionality for the user. One HARQ entity supports multiple HARQ processes. The HARQ entity handles all HARQ related functionalities required. The multiplexing entity is responsible for concatenating multiple MAC-d PDUs into MAC-es PDUs, and to multiplex one or multiple MAC-es PDUs into a single MAC-e PDU, to be transmitted at the next TTI, and as instructed by the E-TFC selection function. It is also responsible for managing and setting the TSN per logical channel for each MAC-es PDU. The MAC-e/es entity receives scheduling information from Node B (network side) via Layer 1 signaling as shown in FIG. 5. Absolute grants are received on E-AGCH (Enhanced Absolute Grant Channel), relative grants are received on the E-RGCH (Enhanced Relative Grant Channel).
E-DCH MAC Architecture—UTRAN Side
An exemplary overall UTRAN MAC architecture is shown in FIG. 6. The UTRAN MAC architecture includes a MAC-e entity and a MAC-es entity. For each UE that uses an E-DCH, one MAC-e entity per Node-B and one MAC-es entity in the S-RNC are configured. The MAC-e entity is located in the Node B and controls access to the E-DCH. Further, the MAC-e entity is connected to MAC-es located in the S-RNC.
In FIG. 7 the MAC-e entity in Node B is depicted in more detail. There is one MAC-e entity in Node B for each UE and one E-DCH scheduler function in the Node-B for all UEs. The MAC-e entity and E-DCH scheduler handle HSUPA (High-Speed Uplink Packet Access) specific functions in Node B. The E-DCH scheduling entity manages E-DCH cell resources between UEs. Commonly, scheduling assignments are determined and transmitted based on scheduling requests from the UEs. The De-multiplexing entity in the MAC-e entity provides de-multiplexing of MAC-e PDUs. MAC-es PDUs are then forwarded to the MAC-es entity in the S-RNC.
One HARQ entity is capable of supporting multiple instances (HARQ processes), e.g. employing a stop and wait HARQ protocols. Each HARQ process is assigned a certain amount of the soft buffer memory for combining the bits of the packets from outstanding retransmissions. Furthermore each process is responsible for generating ACKs or NACKs indicating delivery status of E-DCH transmissions. The HARQ entity handles all tasks that are required for the HARQ protocol.
In FIG. 8 the MAC-es entity in the S-RNC is shown. It comprises the reordering buffer which provides in-sequence delivery to RLC and handles the combining of data from different Node Bs in case of soft handover. The combining is referred to as Macro diversity selection combining.
It should be noted that the required soft buffer size depends on the used HARQ scheme, e.g. an HARQ scheme using incremental redundancy (IR) requires more soft buffer than one with chase combining (CC).
MAC-e PDU Format
As indicated in FIGS. 10 and 11, for an E-DCH there exist two MAC sublayers: MAC-e and MAC-es. The MAC-es layer “sits on top” of MAC-e layer and receives PDUs directly from MAC-d layer on UE side. MAC-es SDUs (i.e. MAC-d PDUs) of same size provided by a particular logical channel may be multiplexed to a single MAC-es payload (SDU=Service Data Unit). This multiplexed payload data is preceded by a MAC-es header. The MAC-es header is also referred to as a framing header. The number of PDUs, as well as the DDI value identifying the logical channel, the MAC-d flow and the MAC-es SDU size are included as part of the MAC-e header. Multiple MAC-es PDUs, but only one MAC-e PDU can be transmitted in a TTI.
The field DDI (Data Description Indicator) field comprises a specific DDI value indicating that whether there is more than one MAC-es PDU included in the MAC-e PDU. This header will not be associated with a new MAC-es payload.
Packet Scheduling
Packet scheduling may be a radio resource management algorithm used for allocating transmission opportunities and transmission formats to the users admitted to a shared medium. Scheduling may be used in packet based mobile radio networks in combination with adaptive modulation and coding to maximize throughput/capacity by e.g. allocating transmission opportunities to the users in favorable channel conditions. The packet data service in UMTS may be applicable for the interactive and background traffic classes, though it may also be used for streaming services. Traffic belonging to the interactive and background classes is treated as non real time (NRT) traffic and is controlled by the packet scheduler. The packet scheduling methodologies can be characterized by:                Scheduling period/frequency: The period over which users are scheduled ahead in time.        Serve order: The order in which users are served, e.g. random order (round robin) or according to channel quality (C/I or throughput based).        Allocation method: The criterion for allocating resources, e.g. same data amount or same power/code/time resources for all queued users per allocation interval.        
In 3GPP UMTS R99/R4/R5, the packet scheduler for uplink is distributed between Radio Network Controller (RNC) and user equipment (UE). On the uplink, the air interface resource to be shared by different users is the total received power at a Node B, and consequently the task of the scheduler is to allocate the power among the user equipment(s). In current UMTS R99/R4/R5 specifications the RNC controls the maximum rate/power a user equipment is allowed to transmit during uplink transmission by allocating a set of different transport formats (modulation scheme, code rate, etc.) to each user equipment.
The establishment and reconfiguration of such a TFCS (transport format combination set) may be accomplished using Radio Resource Control (RRC) messaging between RNC and user equipment. The user equipment is allowed to autonomously choose among the allocated transport format combinations based on its own status e.g. available power and buffer status. In current UMTS R99/R4/R5 specifications there is no control on time imposed on the uplink user equipment transmissions. The scheduler may e.g. operate on transmission time interval basis.
E-DCH—Node B Controlled Scheduling
Node B controlled scheduling is one of the technical features for E-DCH which may enable more efficient use of the uplink resources in order to provide a higher cell throughput in the uplink and may increase the coverage. The term “Node B controlled scheduling” denotes the possibility for a Node B to control uplink resources, e.g. the E-DPDCH/DPCCH power ratio, which the UE may use for uplink transmissions on the E-DCH within limits set by the S-RNC. Node B controlled scheduling is based on uplink and downlink control signaling together with a set of rules on how the UE should behave with respect to this signaling.
In the downlink, a resource indication (scheduling grant) is required to indicate to the UE the (maximum) amount of uplink resources it may use. When issuing scheduling grants, the Node B may use QoS-related information provided by the S-RNC and from the UE in the scheduling requests to determine the appropriate allocation of resources for servicing the UE at the requested QoS parameters.
For the UMTS E-DCH, there are commonly two different UE scheduling modes defined depending on the type of scheduling grants used. In the following the characteristics of the scheduling grants are described.
Scheduling Grants
Scheduling grants are signaled in the downlink in order to indicate the (maximum) resource the UE may use for uplink transmissions. The grants affect the selection of a suitable transport format (TF) for the transmission on the E-DCH (E-TFC selection). However, they usually do not influence the TFC selection (Transport Format Combination) for legacy dedicated channels.
There are commonly two types of scheduling grants which are used for the Node B controlled scheduling:                absolute grants (AGs), and        relative grants (RGs)        
The absolute grants provide an absolute limitation of the maximum amount of uplink resources the UE is allowed to use for uplink transmissions. Absolute grants are especially suitable to rapidly change the allocated UL resources.
Relative grants are transmitted every TTI (Transmission Time Interval). They may be used to adapt the allocated uplink resources indicated by absolute grants by granular adjustments: A relative grant indicates the UE to increase or decrease the previously allowed maximum uplink resources by a certain offset (step).
Absolute grants are only signaled from the E-DCH serving cell. Relative grants can be signaled from the serving cell as well as from a non-serving cell. The E-DCH serving cell denotes the entity (e.g. Node B) actively allocating uplink resources to UEs controlled by this serving cell, whereas a non-serving cell can only limit the allocated uplink resources, set by the serving cell. Each UE has only one serving cell.
Absolute grants may be valid for a single UE. An absolute grant valid for a single UE is referred to in the following as a “dedicated grant. Alternatively, an absolute grant may also be valid for a group of or all UEs within a cell. An absolute grant valid for a group of or all UEs will be referred to as a “common grant” in the following. The UE does not distinguish between common and dedicated grants.
Relative grants can be sent from serving cell as well as from a non-serving cell as already mentioned before. A relative grant signaled from the serving cell may indicate one of the three values, “UP”, “HOLD” and “DOWN”. “UP” respectively “DOWN” indicates the increase/decrease of the previously maximum used uplink resources (maximum power ratio) by one step. Relative grants from a non-serving cell can either signal a “HOLD” or “DOWN” command to the UE. As mentioned before relative grants from non-serving cells can only limit the uplink resources set by the serving cell (overload indicator) but can not increase the resources that can be used by a UE.
UE Scheduling Operation
This sections only outlines the principal scheduling operation, more details on the scheduling procedure is provided in 3GPP TS25.309.
The UE maintains a Serving Grant (SG) which is common to all HARQ process, which indicates the maximum power ratio (E-DPDCH/DPCCH) the UE is allowed for the E-TFC selection. The SG is updated by the scheduling grants signaled from serving/non-serving cells. When the UE receives an absolute grant from the serving cell the SG is set to the power ratio signaled in the absolute grant. The absolute grant can activate/deactivate a single or all HARQ processes. As already mentioned before, an absolute grant can be received on primary or secondary E-RNTI. There are some precedence rules for the usage of primary/secondary absolute grants. A primary absolute grant always affects the SG immediately. Secondary absolute grants only affect the SG if the last primary absolute grant deactivated all HARQ processes, or if the last absolute grant that affected the SG was received with the secondary E-RNTI. When the transmission from primary to secondary E-RNTI is triggered, by deactivating all HARQ processes, the UE updates the Serving Grant with the latest received absolute grant on the secondary E-RNTI. Therefore UE needs to listen to both primary and secondary E-RNTIs.
When no absolute grant is received from the serving cell the UE shall follow the relative grants from the serving cell, which are signaled every TTI. A serving relative Grant is interpreted relative to the UE power ratio in the previous TTI for the same hybrid ARQ process as the transmission, which the relative Grant will affect. FIG. 9 illustrates the timing relation for relative grants. The assumption here is that there are 4 HARQ processes. The relative grant received by the UE, which affects the SG of the first HARQ process, is relative to the first HARQ process of the previous TTI (reference process). Since a synchronous HARQ protocol is adopted for E-DCH the different HARQ processes are served successively.
The UE behavior in accordance to serving E-DCH relative grants is shown in the following:                When the UE receives an “UP” command from Serving E-DCH RLS                    New SG=Last used power ratio+Delta                        When the UE receives a “DOWN” command from Serving E-DCH RLS                    New SG=Last used power ratio−Delta                        
The “UP” and “DOWN” command is relative to the power ratio used for E-DCH transmission in the reference HARQ process. The new Serving Grant (SG) for all HARQ processes, affected by the relative grant, is an increase respectively decrease of the last used power ratio in the reference HARQ process. The “HOLD” command indicates that the SG remains unchanged.
As already mentioned before a Node B from a non-serving RLS is only allowed to send relative grants, which can either indicate a “HOLD” or “DOWN”. The “DOWN” command enables non-serving cells to limit the intercell-interference caused by UEs which are in SHO with these non-serving cells. The UE behavior upon reception of non-serving relative grants is as follows:                When the UE receives a “DOWN” from at least one Non-serving E-DCH RLS                    new SG=Last used power ratio−Delta                        
Relative grants from a non-serving RLS affect always all HARQ processes in the UE. The amount of reduction of the used power ratio might be static or depending on the bit rate, for higher bit rates there might be a larger step size (Delta).
When the UE receives a scheduling grant from the serving RLS and a “DOWN” command from at least one non-serving RL:                new SG=minimum(last used power ratio-delta, received AG/RG from serving RLS)Rate Request Signaling        
In order to enable Node B to schedule efficiently while considering also the QoS requirements of a service mapped on the E-DCH, an UE provides the Node B information on its QoS requirements by means of rate request signaling.
There are two kinds of rate request signaling information on the uplink: the so called “happy bit”, which is a flag related to a rate request on the E-DPCCH and the scheduling information (SI), which is commonly sent in-band on the E-DCH.
From a system point of view, the one-bit rate request may be advantageously used by the serving cell to effect small adjustments in the resource allocation for example by means of relative grants. On the contrary, scheduling information may advantageously be employed for making longer term scheduling decisions, which would be reflected in the transmission of an absolute grant. Details on the two rate request signaling methods are provided in the following.
Scheduling Information Sent on E-DCH
As mentioned before the scheduling information should provide Node B information on the UE status in order to allow for an efficient scheduling. Scheduling information may be included in the header of a MAC-e PDU. The information is commonly sent periodically to Node B in order to allow the Node B to keep track of the UE status. E.g. the scheduling information comprises following information fields:                Logical channel ID of the highest priority data in the scheduling information        UE buffer occupancy (in Bytes)                    Buffer status for the highest priority logical channel with data in buffer            Total buffer status                        Power status information                    Estimation of the available power ratio versus DPCCH (taking into account HS-DPCCH). UE should not take power of DCHs into account when performing the estimation                        
Identifying the logical channel by the logical channel ID from which the highest priority data originates may enable the Node B to determine the QoS requirements, e.g. the corresponding MAC-d flow power offset, logical channel priority or GBR (Guaranteed Bit Rate) attribute, of this particular logical channel. This in turn enables the Node B to determine the next scheduling grant message required to transmit the data in the UE buffer, which allows for a more precise grant allocation. In addition to the highest priority data buffer status, it may be beneficial for the Node B to have some information on the total buffer status. This information may help in making decisions on the “long-term” resource allocation.
In order for the serving Node B to be able to allocate uplink resources effectively, it needs to know up to what power each UE is able to transmit. This information could be conveyed in the form of a “power headroom” measurement, indicating how much power the UE has left over on top of that what is used for DPCCH transmissions (power status). The power status report could also be used for the triggering of a TTI reconfiguration, e.g. switching between 2 ms and 10 ms TTI and vice versa.
Happy Bit
As already explained above the happy bit denotes a one-bit rate request related flag, which is sent on the E-DPCCH. The “happy bit” indicates whether the respective UE is “happy” or “unhappy” with the current serving grant (SG).
The UE indicates that it is “unhappy”, if both of the following criteria are met:                Power status criterion: UE has power available to send at higher data rates (E-TFCs) and        Buffer occupancy criterion: Total buffer status would require more than n TTIs with the current Grants (where n is configurable).        
Otherwise, the UE indicates that it is “happy” with the current serving grant.
Scheduled and Non-Scheduled Data Transmission
In a common UMTS system, there are two categories (or types) of data transmissions for Enhanced Uplink (utilizing an EDCH), scheduled and non-scheduled transmissions.
For scheduled data transmissions, the UE requires a valid scheduling grant before transmitting data on E-DCH. The usual procedure is that UE sends a rate request to the serving Node B by means of either scheduling information or happy bit. Upon reception of the rate request serving Node B allocates uplink resources by means of scheduling grants, i.e. absolute and relative grants, to the UE.
In case of non-scheduled data transmission, the UE is allowed to send E-DCH data at any time, up to a configured number of bits, without receiving any scheduling command from the Node B. Thus, signaling overhead and scheduling delay may be minimized. The resource for non-scheduled transmission is given by the RRC entity (usually the S-RNC) in terms of a maximum number of bits the UE is allowed include in a MAC-e PDU for transmission in a TTI, and is called non-scheduled grant. A non-scheduled grant is may be defined per MAC-d flow. Consequently, logical channels mapped to a non-scheduled MAC-d flow may only transmit up to the non-scheduled grant configured for the respective MAC-d flow. In order to allow the Node Bs serving a particular UE to take into account the possible rise over thermal (RoT) resulting from the UE due to the transmission of non-scheduled data, the Node B(s) is/are informed on the non-scheduled grants assigned to the UE via NBAP signaling (Node B Application Part signaling) from the UTRAN. The UE receives the non-scheduled grants via RRC signaling. There is a set of rules defining the handling of non-scheduled and scheduled data flows.                The UTRAN may restrict a non-scheduled MAC-d flow to use only a limited number of HARQ processes in case of 2 ms TTI (so called HARQ process restriction). For non-scheduled grants, a Node B has always to reserve the configured resources, i.e. maximum number of bits, in its scheduling decisions.        
In order to limit the amount of resources, which may be fairly significant especially for the 2 ms TTI case, the Node B has to permanently reserve for non-scheduled transmissions, the UTRAN (commonly the S-RNC) can disable certain HARQ processes for non-scheduled MAC-d flows. The allocation of HARQ processes for non-scheduled MAC-d flows is configured via RRC signaling.                UTRAN may also reserve some HARQ processes for non-scheduled transmission (i.e. scheduled data cannot be sent using these processes, the processes are considered disabled) in case of 2 ms TTI.        Multiple non-scheduled MAC-d flows may be configured in parallel by the S-RNC and may be multiplexed to a single transport channel for transmission using one of the available HARQ processes. In this case, the UE is commonly allowed to transmit non-scheduled data up to the sum of bits indicated by the corresponding non-scheduled grant, if several MAC-d flows are multiplexed in a TTI.        Scheduled grants will be considered on top of non-scheduled transmissions        Logical channels mapped on a non-scheduled MAC-d flow cannot transmit data using a valid Scheduling Grant.        
As can be seen from the rules, the resource allocation from UTRAN side is separated by assigning scheduled and non-scheduled grants to the UEs. Also within the UE the allocation of resources to logical channels is done in accordance to scheduled and non-scheduled grants. Logical channels will be served in the order of their priorities until the non-scheduled grants and scheduled grants are exhausted, or the maximum transmit power is reached.
Transport Channels and E-TFC Selection
In third generation mobile communication systems, data generated at higher layers is commonly transmitted via the air interface using so-called transport channels, which are mapped to different physical channels in the physical layer. Transport channels are services offered by the physical layer to Medium Access Control (MAC) layer for information transfer. The transport channels are primarily divided into two types:                First, common transport channels requiring an explicit identification of the receiving UE. This type of transport channel may for example be used, if the data on the transport channel is intended for a specific UE or a sub-set of all UEs (no UE identification is needed for broadcast transport channels).        Second, dedicated transport channels, where the receiving UE is implicitly identified by the physical channel carrying the transport channel        
The E-DCH is a dedicated transport channel. The data is transmitted via a transport channel in transport blocks, wherein there is one transport block transmitted in a given time interval, referred to as a transmission time interval (TTI). A transport block is the basic data unit exchanged over transport channels, i.e. between the physical layer and MAC layer. Transport blocks arrive to or are delivered by the physical layer once every TTI. In case of transmissions via the E-DCH a transport block corresponds to a MAC-e PDU.
Enhanced transport format combination (E-TFC) restriction/selection is the procedure in which the UE selects the amount of data to transmit within a transmission time interval (TTI). The aim of the E-TFC selection process is to transmit as many data as possible with the transmit power available to the UE. The E-TFC restriction process considers the amount of transmission power remaining for E-DCH transmissions after transmission of data on DCH channels and HS-DPCCH and eliminates transmission formats due to power limitation. The E-TFC selection procedure, which is responsible for the selection of an appropriate transport format for the transmission of data on E-DCH as described before, is invoked by the HARQ entity in MAC-e/es. The E-TFC restriction procedure, which is described in 3GPP TS 25.133: “Requirements for support of radio resource management (FDD)” in more detail.
For each MAC-d flow multiplexed to a transport channel, radio resource control RRC configures the MAC layer with a HARQ profile and a multiplexing list. The HARQ profile includes the power offset and maximum number of HARQ transmissions to use for a respective MAC-d flow. The multiplexing list identifies for each MAC-d flow, the other MAC-d flows from which data can be multiplexed in a transmission that uses the power offset included in its HARQ profile.
RRC may control the scheduling of uplink data by giving each logical channel a priority (for example between 1 and 8, where 1 is the highest priority and 8 the lowest). E-TFC selection in the UE is commonly done in accordance with the priorities indicated by RRC. Logical channels have absolute priority, i.e. the UE may maximize the transmission of higher priority data.
RRC may further allocate non-scheduled transmission grants to individual MAC-d flows in order to reduce the transmission delays. Each non-scheduled grant is applicable for a specific set of HARQ processes indicated by RRC as already mentioned above. RRC may also restrict the set of HARQ processes for which scheduled grants are applicable.
For each configured MAC-d flow, a given E-TFC can be in any of the following states:                Supported state        Blocked state        
At each TTI boundary, the UEs with an E-DCH transport channel configured may determine the state of each E-TFC for every MAC-d flow configured based on its required transmit power versus the maximum UE transmit.
Further, at every TTI boundary for which a new transmission is requested by the HARQ entity, i.e. in case of retransmissions no E-TFC selection is performed, the UE may perform the operations described in the following. For an E-DCH in UMTS, the Scheduling Grant provides the E-TFC selection function with the maximum E-DPDCH to DPCCH ratio that the UE is allowed to allocate for the upcoming transmission time interval for scheduled data. Based on the HARQ process ID and the RRC configuration, the UE determines whether to take the scheduled and non-scheduled grants into account for the transmission in the upcoming transmission time interval. If for example a non-scheduled grant is disabled (inactive) for the HARQ process ID used in the upcoming transmission time interval, then this non-scheduled grant is assumed to not exist, i.e. set to zero.
The transmission format and data allocation process done during E-TFC selection may inter alia follow the requirements below:                Only the data from logical channels for which a non-zero grant is available may be considered as available;        The data allocation should maximize the transmission of higher priority data;        The amount of data from MAC-d flows for which non-scheduled grants were configured may not exceed the value of the non-scheduled grant;        The total amount of data from MAC-d flows for which no non-scheduled grants were configured shall not exceed the largest payload that can be transmitted based on the Scheduling Grant and the power offset from the selected HARQ profile; In the case where the HARQ process is inactive, the UE shall not include any such data in the transmission;        Only E-TFCs in supported state shall be considered;        
Once an appropriate E-TFC and data allocation are found, the “Multiplexing and TSN Setting” entity generates a MAC-e PDU which is passed to the HARQ process identified by the HARQ process ID for transmission.
The E-TFC selection function shall provide this MAC-e PDU and transmission HARQ profile to the HARQ entity. The HARQ entity shall also be informed of whether the transmission includes Scheduling Information.
Summarizing, in the UMTS system currently discussed by the 3GPP, data transmitted on an E-DCH are categorized in scheduled data and non-scheduled data. As described before, MAC-e control signaling like framing headers or Scheduling Information (SI) needs to be accounted for by the E-TFC selection procedure. Scheduling Information are thereby handled as non-scheduled data for which a valid non-scheduled grant is assumed. The introduction of a HARQ process restriction allows a Node B to only reserve resources for non-scheduled data transmissions for particular HARQ processes. However, the newly introduces HARQ process restriction for non-scheduled data on the other hand creates new problems, as for example Scheduling Information handled as non-scheduled data may only be transmitted in the processes for which the non-scheduled grant is valid. This may imply a significant delay to the signaling of scheduling information resulting in a scheduling delay. Delayed scheduling decisions by the serving Node B will in turn reduce the uplink throughput and thereby degrades the quality of service QoS experienced for the different services, which is especially critical, if certain QoS requirements need to be met by a service.